1. Field of the Invention
The present invention relates to a grinding machine capable of grinding outer and inner surfaces of workpieces and, more particularly, to a grinding machine provided, on its indexable wheel head, with an outer surface grinding wheel, an inner surface grinding wheel and a measuring device for detecting the position of a reference surface of a workpiece.
2. Description of the Prior Art
A known grinding machine for outer surface grinding is provided with a table movable along a horizontal direction, a spindle head mounted on the table so as to rotate a workpiece about an axis parallel to the moving direction of the table, a wheel head movable along a direction perpendicular to the moving direction of the table, an outer surface grinding wheel supported on the wheel head, and a measuring device having a touch probe engagable with a reference shoulder surface of the workpiece. In such grinding machine, the table is moved to cause the touch probe of the measuring device to engage with the reference surface of the workpiece, and the position of the table is detected when the touch probe engages with the reference surface. The table is then relatively moved from the detected position in accordance with a numerical control program so as to grind the outer surface of the workpiece. With this arrangement, the outer surface of the workpiece is accurately machined regardless of the positional deviation of the workpiece with respect to the table.
On the other hand, a known grinding machine capable of grinding both outer and inner surfaces is provided with an outer surface grinding wheel and a inner surface grinding wheel on its indexable wheel head.
In such grinding machines, however, it is difficult to grind inner surface precisely, if a position measuring device for detecting the axial position of a workpiece is not provided for the inner surface grinding wheel other than a position measuring device for the outer surface grinding wheel because the measuring device for the outer surface grinding wheel is mounted on the indexable wheel head at its front side at which the outer surface grinding wheel is also supported, and the inner surface grinding wheel is supported on the opposite side of the wheel head. Therefore, it is necessary to provide two position measuring devices in order to grind both inner and outer surfaces of the workpiece, so that the structure of the grinding machine becomes complex.